High speed varifocal objective system

ABSTRACT

A zoom-type objective system designed for Super-8 motion-picture cameras includes a fixed-focus basic objective and a varifocal front attachment with two fixed positive components bracketing two axially movable negative components. The attachment and the basic objective are separated by a reflex prism which may be removed to enable relocation of the basic objective into a forward position suitable for close-ups. Several combinations of the same basic objective with different attachments are disclosed, the interchange of certain of these attachments enabling a modification of the zoom range.

United Stat Macher [111 3,820,876 June 28, 1974 HIGH-SPEED VARIFOCALomncrrvn' SYSTEM Inventor: Karl Macher, Bad Kreuznach,

Germany Assignee: Jos. Schneider & Co. Optische Werke, Bad Kreuznach,Germany Filed: Dec. 26, 1972 Appl. No.: 318,163

Foreign Application Priority Data oecfzs, 1971 Germany 2164937 US. Cl.350/184, 350/214 Int. Cl. G02b 15/16 Field of Search 350/184, 186

References Cited UNITED STATES PATENTS 10/1967 Macher 350/184 5/1969Macher 350/184 X d4 draw u r:

FOREIGN PATENTS OR APPLICATIONS 8 16,024 4/1971 Japan 350/184 PrimaryExaminer-John K. Corbin Attorney, Agent, or Firm-Karl F. Ross; HerbertDubno [57] ABSTRACT A zoom-type objective system designed for Super-8motion-picture cameras includes a fixed-focus basic objective and avarifocal front attachment with two fixed positive components bracketingtwo axially movable negative components. The attachment and the basicobjective are separated by a reflex prism which may be removed to enablerelocation of the basic objective into a forward position suitable forclose-ups. Several combinations of the same basic objective withdifferent attachments are disclosed, the interchange of certain of theseattachments enabling a modification of the zoom range.

8 Clains, 14 Drawing Figures PATENTEfl-uuuea m4 3320.876

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HIGH-SPEED VARIFOCAL OBJECTIVE SYSTEM FIELD OF THE INVENTION My presentinvention relates to a high-speed objective system of variable focallength, comprising a fixedfocus basic objective and a varifocal frontattachment with two axially movable components.

BACKGROUND OF THE INVENTION Varifocal objective systems of this generaltype have been disclosed in a number of commonly owned U.S. Patst,including Nos. 3,057,257, 3,273,457 and 3 ,457,003. In each case thebasic multilens objective or rear lens group consists of four air-spacedsinglets, all but the third of them being positively refracting, whereasthe attachment or front lens group has two fixed positive componentsbracketing two axially movable negative components. As appliedparticularly to the first component of the attachment, the term fixeddoes not exclude limited adjustability for focusing purposes, as is wellunderstood in the art.

As is likewise known from some of these prior patents, a reflex prismmay be inserted between the two lens groups, preferably ahead of adiaphragm so as to permit full use of a viewfinder even with thediaphragm closed.

Objects of the Invention The general object ofmy present invention is toprovide an improved objective system of this nature which has a largerelative aperture, such as l 1.8, and is highly corrected so that itsresidual distortions in any zoom position are no greater than those of agood fixed-focus objective of the same focal length.

A more particular object of my invention is to provide an objectivesystem of this character which is especially adapted for use with homemovie cameras, such as those of the Super-8 type.

It is also an object of this invention to provide a plurality ofvarifocal attachments interchangeably usable with the same basicobjective to establish several optically equivalent systems of differentzoom ranges.

Summmary of the Invention Let f,, f f and f designate the individualfocal lengths of the positive first component, the negative secondcomponent, the negative-third component and the positive fourthcomponent, respectively, of the varifocal front group and let fy be thefocal length of the basic objective or rear group. The system accordingto my invention then satisfies the following relationships:

More particularly, in keeping with the specific examples givenhereinafter,

The relative order of magnitude of the individual focal lengths of theseveral components is as follows:

f1 lfml f1v fv |fll|- The first (positive) component consists of anegative front lens followed by one or more positive lenses with aseparation which is a small fraction of the individual focal length f,of that component, i.e., less than 10 percent of that focal length. Thenegative second component consists of two air-spaced dispersive lensmembers, either of which could be cemented. The third and fourthcomponents are single lens members of negative or positive refractivity,respectively, which could also be of the compound type. The individualback-focal length of the first and the second component exceeds 0.9times the corresponding focal length f, and I f j, respectively.

Such systems can be designed with varifocal ratios ranging between 3 land ll l. The several varifocal attachments affording these differentratios all have the same overall back-focal length and differ in theirphysical axial length by less than 3 2 so that their mutual substitutionrepresents no major problem. The position of the diaphragm and theshutter need not be changed upon such substitution of attachments. Theradii of curvature of all lens surfaces are larger than the minimumfocal length so that their manufacture is not particularly expensive. Afavorable position of the entrance pupil allows convenient dimensioningof the objective housing. Distortion is at a minimum in all operatingpositions.

Upon removal of the reflex prism it is possible to shift the basicobjective into a forward position in which close-ups can be takeninasmuch as the image plane for short object distances then coincideswith the normal focal plane of the system.

The basic objective and the interchangeable attachments can beconstructed in modular form for easy emplacement and removal.

BRIEF DESCRIPTION OF THE DRAWING SPECIFIC DESCRIPTION In FIG. 1 I haveshown an optical objective system comprising a front attachment withfour components I, II, III, IV, a reflex prism P and a basic objectiveV. Components II and III, which are of negative refractivity, areaxially movable to change the overall focal length f between a minimumvalue f and a maximum value f these components have been illustrated inan intermediate position f of adjustment. All the other components areconsidered stationary, except that front component I (or a part thereof)may be limitedly adjustable for focusing purposes and basic objective Vmay be shiftable into a forward position, adjacent rear component IV ofthe varifocal attachment, upon removal of the reflex prism P. The systemalso includes a diaphragm D, shown in FIGS. 4-7, as well as anonillustrated shutter alongside that diaphragm between prism P andbasic objective V. A conventional viewfinder, not shown, receives thelight rays reflected at an internal semitransparent surface of a body L7constituting the prism P.

Front component I consists of a first lens L1 in the form of a negativemeniscus, with radii rl, r2 and thickness d1, and a positive lens L2(radii r3, r4 and thickness d3) separated from lens Ll by an air spacea2. A variable air space 114 separates lens L2 from a negative meniscusL3 (radii rs, r6 and thickness d) representing the first member ofcomponent II; the second member of that component, separated from lensL3 by an air space d6, is a nearly planoconcave lens L4 of radii r7, r8and thickness d7. Another variable air space d8 intervenes between lensL4 and a negative lens L5 (radii r9, r10 and thickness d9), alsomeniscus-shaped, which represents the third component III. Betwen thelatter component and a biconvex lens L6 (radii r11 and r12 and thicknessdll constituting the fourth component IV, there exists a furthervariable air space dl0. Prism body L7, whose planar end faces (ofinfinite radius) have been indicated at r13 and r14, has a thickness(113 and is separated from lens L6 by an air space 1112; an air spacedl4 exists between this prism body and the biconvex first lens L8 (radiir15, r16 and thickness (115) of basic objective V which is followedafter an air space dl6 by a positive meniscus L9 (radii r17, r18 andthickness dl7); the third member of the basic objective is anasymmetrical biconcave lens L10 (radii r19, r20 and thickness dl9) whichis separated by respective air spaces (118 and (120 from lens L9 andfrom a final lens Lll (radii r21, r22 and thickness d2l) of biconvexshape.

Table 1 gives representative numerical values, in suitable linear unitssuch as millimeters, for the radii r1-r22 and the thicknesses andseparations dl-d2l of the system of FIG. 1 which has a relative apertureof 1:18, a varifocal ratio of 1:3 (f l0,f,, and

a back-focal length of 13.05. Also given in the Table are the refractiveindices n and the Abbe numbers 1 of the lens glasses, based upon thegreen E line of the spectrum, as well as the surface powers An/rassociated with the several radii. The surface powers may vary within atolerance range 0.01 f lf the tolerance range for'the lens spacings is$0.4 f whereas the refractive indices n and the Abbe numbers v may varyby 10.02 and by :10 percent, respectively. These tolerances apply alsoto all other embodiments as well as to the corresponding valuesappearing in the appended claims. The variable distances d4, d8 and dl0of Table l are given for an overall focal length f 20.

TABLE 1 Lenses Radii Thicknesses n, v, An/r and separations rl=+4l 42+0.0l9l LII dl=l.80 l.79l7 25.8

d2=4.50 air space r3==+27 O5 +0.025l L2 (13%.00 1.6808 54.9

TABLE l.-Continued Lenses Radii Thicknesses n, v, An/r arg @FPQ P' 'Q 5d4==l6.32 air space (variable) r5= +2727.00 +0.000l L3 d5=l.00 1.489l70.2

d6=3.70 air space r7=-29.74 0.0 I 64 L4 d7=l.00 1.489! 70.2 10 rs=-+2794o 0.00|1

air space (variable) di -l8 46 -0.0264 L5 d9=l.00 1.489! 70.2

rl0=70 l5 +0.0069

dl0=4.24 air space (variable) rll=+60.03 +0.0] ll 15 L6[ dll=2.40 I.67l34L6 dl2=3. 10 air space r13= 120.0 L7 d13=9.00 l.5l87 63.9

dl4=4.50 air space 20 rl5=+22 56 +0.0307

L8 dl5=2.55 1.6940 54.4

rl6=l06 20 +0.0065

l6=0.05 air space rl7=+l3 29 +0.0522 L9 dl7=l 1.6940 54.4

rl8==+30.04 -0.023l 25 dl8=l .40 air space 9=36.l9 0.0224 L10 dl9=4.901.8!26 25.2

0.0739 0=2.25 air space r2l=+32 69 +0.02l9

d2l=2.45 1.716] 53.6 30 r22=+l4 +0.0490

In FIG. 1A I have shown the relative variation of air 35 spaces d4, d8and dl0 over the entire zoom range. Spef 10.3 0.l5 27.05 2.10 l5.0 9.9615.62 3.72 20.0 16.31 8.75 4.24 25.0 20.68 4.72 3.90 30.0 23.91 2.4!2.98

The individual focal lengths for the system of FIG. 1 and Table 1 are asfollows:

same relative aperture, back-focal length and varifocal.

r'atio as that of Table 1 and also has almost the same overall axiallength 2d. Variable air spaces d4, d8 and dl0 are again given for anintermediate focal length fmed 20.

5 TABLE 2 Lenses Radii Thicknes'ses n, u, An]! and separationsrl=-1-l92.35 +0.0039 L1 I d =1.80 1.7616 27.3

d2==2.50 air space r2a=+44 .43 +0.01 38 L2a I d2a=4.00 1.6167 54.8

d2b=0. 10 air space r3b=l-37.56 +0.0164 L2 d3b=3.80 1.6176 50.8

:0.0 d4=16.54 air space (variable) r5=+2727.00 +0.0001 L3 I d5=1.001.4891 70.2

d6=3.70 air space r7='32.50 0.0150 L4 d7=l.00 1.4891 70.2

d8=8.55 air space (variable) r9=l 8 46 0.0264 L5 d9=l.00 1.4891 70.2

d10=4.31 air space (variable) r1 l=+60.03 +0.01l1 L6[ dll=2.40 1.671341.6

d12=3.10 air space rl 10.0 L7 dl3=9.00 1.5187 63.9

10.0 dl4=4.50 air space r15=+22 56 +0.0307 L8 d1$=2.55 1.6940 54.4

d16=0.05 air space rl7=+l3 29 +0.0522 L9 d17=1.80 1.6940 54.4

dl8=1.40 air space r19=36 19 0.0224 L10[ d19=4.90 1.8126 25.2

d 0=2.25 air space r2l=+32 69 +0.0219 L11 d2l=2.45 1.7161 53.6

FIG. 2A shows the law of variation of air spaces d4, J8 and d 10throughout the zoom range in the system of FIG. 2. Representativenumerical values for five focal lengths are as follows:

f d4 8 d10 10.2 0.06 27.26 2.08 15.0 10.17 15.45 3.78 20.0 16.54 8.554.31 25.0 20.92 4.49 3.99 30.0 24.16 2.17 3.07

The individual focal lengths for this system are the same as in thefirst embodiment.

In FIG. 3 1 have shown a system similar to that of FIG. 2, except for areplacement of the singlet L4 in component 11 by a doublet consisting ofa positive lens L4a (radii r7a, r7b and thickness (17a) and a negativelens L4b (radii r7b, r8b and thickness d7b).

Reference is made to Table 3 for the parameters of the system of FIG. 3.This system has the same varifocal ratio, relative aperture, back-focallength, overall axial length and intermediate focal lengthfmd as thepreceding one.

6 TABLE 3. -Contrnued Lenses Radii Thicknesses n, u. An/r andseparations d2=2.50 air space r2a=l-43.00 +0.0141 LZa d2a=4.00 1.609956.3

d .10 air space dbl-35.96 +0.0173 L2b d3b=3.80 1.6254 56.6

d4=15.51 air space (variable) r5=l-11342.00 I +0.0001 L3 d5=1.00 1.622860.0

d6=3.70 air space r7a=43.87 -0.0185 L4a d7a=2.40 1.8126 25.2

+0.0094 L4 d7b=1.00 1.6228 60.0

d8=7.33 air space (variable) r9=-14 0.0360 L5 1.00 1.5120 64.0

rl0=3l 49 +0.0162v l0=4.17 air space (variable) r1l=+60 03 +0.0104 L6 1dl1=2.40 1.6250 52.8

rl2=-29 54 +0.02l1

dl2=3.10 air space r1 $0.0 L7 dl3=9.00 1.5178 63.9

10.0 dl4=4.50 air space rl5=+22 56 +0.0307 L8 l5=2.55 1.6940 54.4

rl6=-l06 20 +0.0065

d16=0.05 air space rl7= H3 29 +0.0522 L9 dl7==l.80 1.6940 54.4

dl8=l .40 air space rl9=36 19 0.0224 L101 dl9=4.90 1.8126 25.2

d20=2.25 air space r2l=+32 69 +0.0219 d2l=2 45 1.7161 53.6

FIG. 3A shows the law of variation of air spaces d4, d8 and d10throughout the zoom range in the system of FIG. 3. Representativenumerical values for five focal lengths are as follows:

f d4 d8 d10 10.2 0.24 24.45 2.31 15.0 9.61 13.55 3.84 20.0 15.50 7.334.17 25.0 19.53 3.84 3.63 30.0 22.50 1.98 2.52

The individual focal lengths for the system of FIG. 3 and Table 3 are asfollows:

focal length of 13.05. The values given in the Table are I forf 18.

TABLE 4 TABLE Lenses Radi'i a'll'lldmklm An/r Lenses Radii 'mickneses n,v, All/r and separations 5 separations rl +l8430 +0.0042 r1=-153.40-0.0050

LI 1 111 -1- L791? LI 1 dl=l.80 1.7684 26.7

d2=2.50 air space d I air space r2at-44. r2a=+1 11.98 40.0055

123 1 d .00 1.6176 50.8 L22. 1 a 1.6228 60.0

rap-401 00 +0005 10 r3a='-l59 6o +0.0039

[0 air space d2b=0. 10 air s cc r3b=+37 18 +0.0166 r3b +l32 70 pa +0004?L2b 1 d3b=5.40 1.6176 50.8 1.2 1 3b=-4.40 1.6255 57.7

r-tb=-550.50 +0.00! I u -13230 +0.0047

d4=l5 44 air space (variable) 13 :0, 10 air space i5= +477 50 +0-00l3r4c=+37.l8 -0 1.3 d5=1.00 1.6228 0.0 1. d4c=4.65 1.6228 60.0

r 8 46 rsc=+102.54 0.0060

db=3.70 air space d4==l5 87 air space (variable) r7a=-43 s7 r$=+l50 08H1004? 1.461 d7a32 2 90 1.8126 25.2 L3 1 1.7161 53.6

L4!) d7b=l.50 1.6228 60.0 d6=3 70 air space 0 9 r8 7 air space(variable) $0092 r7 0'03 o'olm I9? 50 0-0379 L4a 1 r7 ld78-L50 1.643059.8 x0098 L5 1 9=1.00 15120 L4b 1 d7b=3.55 1.8126 25.2

d!0=5.85 a1r space (variable) 8=l0 23 air space (variable) rll=+57 441100099 19=-14 55 L6[ dll=2.40 1.5712 55.8 L51 1.5020 61.2

rl2=27.65 +0.0206 81 +0.0120 r1 dl2= 0 Space w 0 dl0=8.50 air space(variable) rll=I-56 91 +0.0109

L 1 L518? L6 1 d11=2.40 1.6203 54.8

dl44.50 air space dl2=4.30 air space rl5=+22.56 rl3= L8[ dl5=2.55 1.694054.4 1.7 d1 9.

rl6=-l06.20 +0.0065 r14== 3- 00 I 5 I87 63 9 .05 air space d14=4.rl7=+l3 29 +0.0522 =+2 56 50 space +0.0307

L I dl7=l 80 l-6940 L8 1 dl5=2.55 1.6940 54.4

rl8==+30 04 0.0231 rl6=-l06.20 +0.0065

dl8=l .40 a1r space 35 ,05 air space rI9='-36.I9 0.0224 rl7=-+I3.29+0.0522

L10 I d19=4.90 1.8126 25.2 L9 I ]7=| 8() 1 94() 544 1'2 9 0:2 25 airspace rl8=+30 04 I 2 l r2l=+32 69 +00 rl9= 36 gl8-L40 air space 0 0224L11 1 d2l=2.45 1.7161 53.6 UM 1. 25,;

l 2 d +0049) 40 r20==+l0 99 0.0739

89-6 d20=2.25 air space r2l=+32 69 +0.0219 1.111 d2l=2.45 1.7161 53.6FIG. 4A shows the law of variation of air spaces d4, 2 d 98 20 +0049) d8and dl0 throughout the zoom range in the system of FIG. 4.Representative numerical values for five focal lengths are as follows:

d4 d8 dl0 0.27 26.05 3.98 l0.36 l4.4l 5.53 l5.44 9.0] 5.85 21. [8 4.045.08 26.43 L86 2.01

The individual focal lengths for the system of FIG. 4 and Table 4 are asfollows:

(fmln 5/1110: 8), based tion with f 16.

upon an intermediate posi- FIG. 5A shows the law of variation of airspaces d4, d8 and d10 throughout the zoom range in the system of FIG. 2.Representative numerical values for five focal lengths are as follows:

ystem are given The system of FIG. 6 is structurally similar to that ofFIG. 5, except for a reversal of curvature of the cemented surface ofdoublet L4a, L4b corresponding to the showing of FIGS. 3 and 4. Thecorresponding parameters, listed in Table 6, provide a varifocal ratioof TABLE 6 Lenses Radii Thickncsses n, v, An/r and separations r1=155.500.004s L1 I dl=1.80 1.7616 27.3

d2=1.60 air space r2a=l-116.70 +0005} L23 d2a=4.80 1.6228 60.0

r3a= l50.82 +0.0041

d2b=0. 10 air space r3b=+113.50 +0.0054 L2b d3b'4.70 1.6228 60.0

d3c=0.10 air space L2c d4c=4.65 1.6228 60.0

d4=17.66 air space (variable) r5=+150.82 +0.0046 L3 d5= 1.00 1.6940 54.4

d6=3.70 air space r7a=88 36 -0.0091 L4a d7a=3 05 1.8126 25.2

r7b='19 64 +0.0086 L4b I d7b=1.00 1.6430 59.8

d8=10 75 air space (variable) r9=12 73 0.0392 L5 d9=1.00 1.4995 66.7

d10=8.60 air space (variable) r11=+63 02 +0.009S L6 d11=2.40 1.6203 54.8

d12=3 17 air space r13= 10.0 L7[ d13=9.00 1.5187 63.9

d14=4.50 air space rl5=+22.56 +0.0307 L8[ d15=2.55 1.6940 54.4

rl6=l06.20 +0.0065

d16=0.05 air space rl7=+13.29 +0.0s22 L9 d17=1.80 1.6940 54.4

d18=1.40 air space 0.0224 rl9=36. 19 L10 dl9=4.90 1.8126 25.2

d20=2.25 air space r2l=+32.69 +0.0219 L11 d21=2.45 1.7161 53.6

FIG. 6A shows the law of variation of air spaces d4, d8 and D10throughout the zoom range in the system of HG. 6. Representativenumerical values for five focal lengths are as follows:

f d4 as d10 7.1 0.30 30.67 6.03 16.0 17.66 10.75 8.59 32.0 27.65 2.556.80 44.0 31.03 2.37 3.60 56.0 33.04 3.86 0.10

The individual focal lengths for this system are given 5 below:

are the same as before.

TABLE 7 Lenses Radii Thicknesses n, v, An/r and separations r1=137.390.0055 L1[ d1=2.00 1.7616 27.3

d2=1 .80 air space r2a=+188.90 +0.0033 L2a[ d2a=6 85 1.6255 57.7

d2b=0.10 air space r3b=+94 06 +0.0066 L2b d3b=7.20 1.6228 60.0

d3c=0.l0 air space r4c=+48 02 +0.0129 L2c d4c=6.75 1.6228 60.0

d4=18 56 air space (variable) r5=+496 50 +0.0013 L3 d5= 1.00 1.6940 54.4

d6*-4.50 air space r7a=*137.60 0.0059 L4a d7a=5.00 1.8126 25.2

r7b=21.05 +0.0080 L4b d7b=1.00 1.6430 59.8

d8=l 1.87 air space (variable) r9= -14.74 0.0331 L5 d9=1.00 1.4891 70.2

d10=13.58 air space (variable) r1 1 1-46.49 +0.0133 L6 d11=2.40 1.620354.8

d12=3.17 air space r13=== :0.0 L7[ d13=9.00 1.5187 63.9

d14=4.50 air space r15=+22.56 0.0307 L8 d15=2 55 1.6940 54.4

rl6=106 20 r 3 0.0065

.05 air space rl7=+13 29 +0.0522 L9[ d17=1 1.6940 54.4

d18=1.40 air space .19 0.0224 L10[ d19=4.90 1.8126 25.2

d20=2.25 air space r21= +32 69 +0.0219 L11[ 2l=2.45 1.7161 53.6

lengths are as follows:

The individual focal lengths for this system are given below:

I claim:

1. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens with a separation of less than percent of theindividual focal length of said first component; said second componentconsisting of a first and a negative second lens member air-spaced fromeach other; said third component being a third negative lens member;said fourth component being a positive lens member; the individual focallengths f, of said first component, f of said second component, f ofsaid third component, f y of said fourth component and fy of said basicobjective being related to one another as follows:

said basic objective consisting of a positive first singlet, a positivesecond singlet, a negative third singlet and a positive fourth singletair-spaced from one another;

the relative numerical values of the radii r15 r22 and of thethicknesses and separations dlS d2l of said first singlet L8, saidsecond singlet L9, said third singlet L10 and said fourth singlet Lll,the magnitudes of their refractive indices n, and Abbe numbers w and thesurface powers An/r thereof being substantially as given in thefollowing Table:

2. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member;

the relative numerical values of the radii rl r12 and of the thicknessesand separations dl dll of said front lens L1, said positive second lensL2, said first negative lens member L3, said second negative lens memberL4, said third negative lens member L5 and said positive lens member L6,the magnitudes of their refractive indices n, and Abbe number w and thesurface powers An/r thereof being substantially as given in thefollowing Table:

3. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member;

said first component including a positive third lens L2b following saidpositive second lens L2a, the

relative numerical values of the radii r1 r12 and of the thicknesses andseparations d1 dll of said front lens Ll, said positive second lens L2a,said positive third lens L2b, said first negative lens member L3, saidsecond negative lens member L4,

' said third negative lens member L5 and said positive lens member L6,the magnitudes of their refractive indices n, and Abbe numbers 11,, andthe surface powers An/r thereof being substantially as given in thefollowing Table:

4. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member;

said first component including a positive third lens L2b following saidpositive second lens L2a, said second negative lens member being adoublet composed of a positive lens L4a and a negative lens L4b, therelative numerical values of the radii r1 r12 and of the thicknesses andseparations d1 d1 1 of said front lens L1, said positive second lensL2a, said positive third lens L2b, said first negative lens member L3,said positive lens L4a, said negative lens L4b, said third negative lensmember L5 and said positive lens member L6, the magnitudes of theirrefractive indices n and Abbe numbers v and the surface powers An/rthereof being substantially as given in the following Table:

14 Continued Lenses Radii Thicknesses n, up Mr and separations L4ad7a=2.40 1.8126 25.2

r7b=r-20.01 +0.0094 b d7b=1.00 1.6228 60.0

' d8=7.33 air space (variable) r9=-l4.20 0.0360 L5 d9=l.00 1.5120 64.0

rl0=31 49 +0.0l62

dl0=4.17 air space (variable) rll=+60.03 +0.0l04 L6 dl l=2.40 1.625052.8

5. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member;

said first component including a positive third lens L2b following saidpositive second lens L2a, said second negative lens member being adoublet composed of a positive lens L4a and a negative lens L4b, therelative numerical values of the radii rl r12 and of the thicknesses andseparations d1 d 11 of said front lens Ll, said positive second lensL2a, said positive third lens L2b, said first negative lens member L3,said positive lens L4a, said negative lens L4b, said third negative lensmember L5 and said positive lens member L6, the magnitude of theirrefractive indices n and Abbe numbers v and the surface power An/rthereof being substantially as given in the following Table:

Lenses Radii Thicknesses n v, An/r and separations rl=+l84.30 +0.0042 Ldl=l 1.7917 25.8

d2=2.50 air space r2a=l-44 l0 +0.0140 L a d2a=5 00 1.6176 50.8

.10 air space r3b= +37 18 40.0166

d3b=5.40 1.6176 50.8 r4b= -5 .50 +0.0011

d4=15 44 air space (variable) r5=+477 s0 +0.0013 L d5=l.00 1.6228 60.0

d6=3.70 air space r7a=--43 87 0.0185 L4a d7a=2.90 1.8126 25.2

r7 +0.0099 L4b d7b= 1.50 1.6228 60.0

.01 air space (variable) r9= 1 3 50 -0.0379 L5 1 1.5120 64.0

l0=5.85 air space (variable) r1l=+57 44 +0.0099 L6[ dll=2 40 1.5712 55.8

6. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member;

said first component including a positive third lens L2b and a positivefourth lens L2c following said positive second lens L2a, said secondnegative lens member being a doublet composed of a negative lens L4a anda positive lens L4b, the relative numerical values of the radii rl r12and of the thicknesses and separations d1 dll of said front lens L1,said positive second lens L2a, said positive third lens L2b, saidpositive fourth lens L2c, said first negative lens member L3, saidnegative lens L4a, said positive lens L4b. said third negative lensmember L and said positive lens member L6, the magnitudes of theirrefractive indices n and Abbe numbers w and the surface powers Art/rthereof being substantially as given in the following Table:

Lenses Radii Thicknesses n, u. An/r and separations r1=l53.40 0.0050 L1dl=1.80 1.7684 26.7

d2=1.80 air space r2a=+l l 1.98 +0.0055 L2a I d2a=4.40 1.6228 60.0

d2b=0.l0 air space r3b=+l32 70 +0.0047 L2b d .40 1.6255 57.7

3c=0.10 air space r4c=+37.l8 10.0167 L20 1 d4c=4.65 1.6228 60.0

d4=l5 87 air space (variable) r5=+150 08 +0.0047 L3 d5==l.00 1.7161 53.6

d6=3.70 air space r7a=60.03 0.0l07 L4a d7a=l 50 1.6430 59.8

r7b= +17.16 +0.0098 L4b[ d7b=3.55 1.8126 25.2

d8=l0 23 air space (variable) r9='14 55 0.0345 L5 d9=1.00 1.5020 61.2

l0=8.50 air space (variable) r11=+56.91 +0.0109 L6 dl1=2.40 1.6203 54.8

7. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member;

said first component including a positive third lens L2b and a positivefourth lens L2c following said positive second lens L2a, said secondnegative lens member being a doublet composed of a positive lens L4a anda negative lens L4b, the relative numerical values of the radii rl r12and of the thicknesses and separations d1 dll of said front lens Ll,said positive lens L2a, said positive third lens L2b, said positivefourth lens L20, said first negative lens member L3, said positive lensL4a, said negative lens L4b, said third negative lens member L5 and saidpositive lens member L6, the magnitudes of their refractive indices n,and Abbe numbers w and the surface powers An/r thereof beingsubstantially as given in the following Table:

Lenses Radii Thicknesses n, v, An/r and separations rl=l55.50 0.0048 L1dl=1.80 1.7616 27.3

d2=l.60 air space r2a=+l 16 +0.0053 L2a d2a=4.80 1.6228 60.0

r3a=-150 82 +0.004l d2b=0. 10 air space r3b=+113 50 +0.0054 L2 1d3b=4.70 1.6228 60.0

d3c=0.10 air space r4c=+37 18 +0.0l67 L2c d4c=4.65 1.6228 60.0

d4=17 66 air space (variable) r5=+150 82 +0.0046 L d5=1.00 1.6940 54.4

. d6=3.70 air space r7a=8 .36 0.0091 L d7a=3.05 1.8126 25.2

r7 +0.0086 1.41) d7b=1.00 1.6430 59.8

r8=+29 l 0.022O

d8=10 air space (variable) r9=-12 73 0.0392 L5 d9=l.00 1.4995 66.7

rl0= 35 96 +0.0l38

dl0=8.60 air space (variable) rll=*1-63 02 +0.0098 L6 dl1=2.40 1.620354.8

8. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens; said second component consisting of a first and anegative second lens member air-spaced from each other; said thirdcomponent being a third negative lens member; said fourth componentbeing a positive lens member; v

said first component including a positive third lens L2b and a positivefourth lens L2c following said positive second lens L2a, said secondnegative lens member being a doublet composed of a positive lens L4a anda negative lens L4b, the relative numerical values of the radii rl r12and of the thickl7 l8 nesses and separations dl dll of said front lensContinued Ll, said positive second lens LZa, said positive Lenses RadThicknessas "e W third lens L2b, said positive fourth lens L2c, said andfirst negative lens member L3, said positive lens Pammns L4a, saidnegative lens L4b, said third negative lens 5 Me I 75 I 6228 60 0 memberL and said positive lensmember L6, the magnitudes of their refractiveindices n and Abbe d4=l 8.56 air space ariable) numbers v,, and thesurface powers An/r thereof L g 00 l 6940 54 4 +000" being substantiallyas given in the following Table: "bi- ,7 0305 l0 d6=4.50 air space r7a=l37.60 0.0059 Lenses Radii Thicknesses n, u, An/r L43 l (171F500 |-3|26and r7b=2l.05 +0.0080 separations L4b d7b=|.00 l.6430 59.8

r8b=+23.27 0.0277 rl=l 37.38 0.0055 d8=l L87 air space (variable) Lldl=2.00 1.76l6 27.3 r9=-14.74 0.033|

r2=+l 10 25 0.0069 Ls d9=l.00 1.489! 70.2

d2=l .80 air space rl0= 56.9l 0()85 rZa=+l 88.90 +0.0033 dl0=l 3.58 airspace (variable) L2a d2a=6.85 1.6255 57.7 rll=+46.49 +0.0l33

r3a=l26.60 +0.0049 L6[ dll=2.40 1.6203 54.8

d2b=0.l0 air space 12=-44,43 +0 3 r3b=+94.06 +0.0066 L2b d3b=7.20 1.622860.0

d3c=0.l0 air space i 4

1. A varifocal objective system comprising a basic multilens objectiveand a varifocal front attachment for said objective, said attachmentbeing composed of a substantially fixed positive first component, anaxially movable negative second component, an axially movable negativethird component and a fixed positive fourth component; said firstcomponent consisting of a negative first lens followed by at least onepositive second lens with a separation of less than 10 percent of theindividual focal length of said first component; said second componentconsisting of a first and a negative second lens member air-spaced fromeach other; said third component being a third negative lens member;said fourth component being a positive lens member; the individual focallengths fI of said first component, fII of said second component, fIIIof said third component, fIV of said fourth component and fV of saidbasic objective being related to one another as follows: 2.5 fV < fI <3fV 0.7 fV < fII < fV 1.75 fV < fIII < 2.5 fV 1.4 fV < fIV < 2 fV fI >fIII > fIV > fV > fII ; said basic objective consisting of a positivefirst singlet, a positive second singlet, a negative third singlet and apositive fourth singlet air-spaced from one another; the relativenumerical values of the radii r15 - r22 and of the thicknesses andseparations d15 - d21 of said first singlet L8, said second singlet L9,said third singlet L10 and said fourth singlet L11, the magnitudes oftheir refractive indices ne and Abbe numbers Nu e, and the surfacepowers Delta n/r thereof being substantially as given in the followingTable: Lenses Radii Thicknesses ne Nu e Delta n/r and separations r15+22.56 +0.0307 L8 (d15 2.55 1.6940 54.4 r16 -106.20 +0.0065 d16 0.05 airspace r17 +13.29 +0.0522 L9 (d17 1.80 1.6940 54.4 r18 +30.04 -0.0231 d181.40 air space r19 -36.19 -0.0224 L10 (d19 4.90 1.8126 25.2 r20 +10.99-0.0739 d20 2.25 air space r21 +32.69 +0.0219 L11 (d21 2.45 1.7161 53.6r22 +14.61 +0.0490
 2. A varifocal objective system comprising a basicmultilens objective and a varifocal front attachment for said objective,said attachment being composed of a substantially fixed positive firstcomponent, an axially movable negative second component, an axiallymovable negative third component and a fixed positive fourth component;said first component consisting of a negative first lens followed by atleast one positive second lens; said second component consisting of afirst and a negative second lens member air-spaced from each other; saidthird component being a third negative lens member; said fourthcomponent being a positive lens member; the relative numerical values ofthe radii r1 - r12 and of the thicknesses and separations d1 - d11 ofsaid front lens L1, said positive second lens L2, said first negativelens member L3, said second negative lens member L4, said third negativelens member L5 and said positive lens member L6, the magnitudes of theirrefractive indices ne and Abbe number Nu e, and the surface powers Deltan/r thereof being substantially as given in the following Table: LensesRadii Thicknesses ne Nu e Delta n/rand separations r1 +41.42 +0.0191 L1(d1 1.80 1.7917 25.8 r2 +24.03 -0.0329 d2 4.50 air space r3 +27.05+0.0251 L2 (d3 6.00 1.6808 54.9 r4 -183.60 +0.0037 d4 16.32 air space(variable) r5 +2727.00 +0.0001 L3 (d5 1.00 1.4891 70.2 r6 +16.99 -0.0287d6 3.70 air space r7 -29.74 -0.0164 L4 (d7 1.00 1.4891 70.2 r8 +279.40-0.0017 d8 8.75 air space (variable) r9 -18.46 -0.0264 L5 (d9 1.001.4891 70.2 r10 -70.15 +0.0069 d10 4.24 air space (variable) r11 +60.03+0.0111 L6 (d11 2.40 1.6713 41.6 r12 -32.91 +0.0203
 3. A varifocalobjective system comprising a basic multilens objective and a varifocalfront attachment for said objective, said attachment being composed of asubstantially fixed positive first component, an axially movablenegative second component, an axially movable negative third componentand a fixed positive fourth component; said first component consistingof a negative first lens followed by at least one positive second lens;said second component consisting of a first and a negative second lensmember air-spaced from each other; said third component being a thirdnegative lens member; said fourth component being a positive lensmember; said first component including a positive third lens L2bfollowing said positive second lens L2a, the relative numerical valuesof the radii r1 - r12 and of the thicknesses and separations d1 - d11 ofsaid front lens L1, said positive second lens L2a, said positive thirdlens L2b, said first negative lens member L3, said second negative lensmember L4, said third negative lens member L5 and said positive lensmember L6, the magnitudes of their refractive indices ne and Abbenumbers Nu e, and the surface powers Delta n/r thereof beingsubstantially as given in the following Table: Lenses Radii Thicknessesne Nu e Delta n/r and separations r1 +192.35 +0.0039 L1 (d1 1.80 1.761627.3 r2 +39.09 -0.0194 d2 2.50 air space r2a +44.43 +0.0138 L2a (d2a4.00 1.6167 54.8 r3a -958.00 +0.0006 d2b 0.10 air space r3b +37.56+0.0164 L2b (d3b 3.80 1.6176 50.8 r4b Infinity + or - 0.0 d4 16.54 airspace (variable) r5 +2727.00 +0.0001 L3 (d5 1.00 1.4891 70.2 r6 +16.99-0.0287 d6 3.70 air space r7 -32.50 -0.0150 L4 (d7 1.00 1.4891 70.2 r8+158.20 -0.0030 d8 8.55 air space (variable) r9 -18.46 -0.0264 L5 (d91.00 1.4891 70.2 r10 -70.15 +0.0069 d10 4.31 air space (variable) r11+60.03 +0.0111 L6 (d11 2.40 1.671341.6 r12 -32.91 +0.0203
 4. A varifocalobjective system comprising a bAsic multilens objective and a varifocalfront attachment for said objective, said attachment being composed of asubstantially fixed positive first component, an axially movablenegative second component, an axially movable negative third componentand a fixed positive fourth component; said first component consistingof a negative first lens followed by at least one positive second lens;said second component consisting of a first and a negative second lensmember air-spaced from each other; said third component being a thirdnegative lens member; said fourth component being a positive lensmember; said first component including a positive third lens L2bfollowing said positive second lens L2a, said second negative lensmember being a doublet composed of a positive lens L4a and a negativelens L4b, the relative numerical values of the radii r1 - r12 and of thethicknesses and separations d1 - d11 of said front lens L1, saidpositive second lens L2a, said positive third lens L2b, said firstnegative lens member L3, said positive lens L4a, said negative lens L4b,said third negative lens member L5 and said positive lens member L6, themagnitudes of their refractive indices ne and Abbe numbers Nu e, and thesurface powers Delta n/r thereof being substantially as given in thefollowing Table: Lenses Radii Thicknesses ne Nu e Delta n/r andseparationsr1 +181.00 +0.0042 L1 (d1 1.80 1.7616 27.3 r2 +38.99 -0.0195d2 2.50 air space r2a +43.00 +0.0141 L2a (d2a 4.00 1.6099 56.3 r3a-451.00 +0.0013 d2b 0.10 air space r3b +35.96 +0.0173 L2b (d3b 3.801.6254 56.6 r4b +641.50 -0.0009 d4 15.51 air space (variable) r5+11342.00 +0.0001 L3 (d5 1.00 1.6228 60.0 r6 +19.23 -0.0323 d6 3.70 airspace r7a -43.87 -0.0185 L4a (d7a 2.40 1.8126 25.2 r7b -20.01 +0.0094L4b (d7b 1.00 1.6228 60.0 r8b +79.77 -0.0078 d8 7.33 air space(variable) r9 -14.20 -0.0360 L5 (d9 1.00 1.5120 64.0 r10 -31.49 +0.0162d10 4.17 air space (variable) r11 +60.03 +0.0104 L6 (d11 2.40 1.625052.8 r12 -29.54 +0.0211
 5. A varifocal objective system comprising abasic multilens objective and a varifocal front attachment for saidobjective, said attachment being composed of a substantially fixedpositive first component, an axially movable negative second component,an axially movable negative third component and a fixed positive fourthcomponent; said first component consisting of a negative first lensfollowed by at least one positive second lens; said second componentconsisting of a first and a negative second lens member air-spaced fromeach other; said third component being a third negative lens member;said fourth component being a positive lens member; said first componentincluding a positive third lens L2b following said positive second lensL2a, said second negative lens member being a doublet composed of apositive lens L4a and a negative lens L4b, the relative numerical valuesof the radii r1 - r12 and of the thicknesses and separations d1 - d11 ofsaid front lens L1, said positive second lens L2a, said positive thirdlens L2b, said first negative lens member L3, said positive lens L4a,said negative lens L4b, said third negative lens member L5 and saidpositive lens member L6, the magnitude of their refractive indices neand Abbe numbers Nu e, and the surface power Delta n/r thereof beingsubstantially as given in the following Table: Lenses Radii Thicknessesne Nu e Delta n/r and separations r1 +184.30 +0.0042 L1 (d1 1.80 1.791725.8 r2 +37.45 -0.0211 d2 2.50 air space r2a +44.10 +0.0140 L2a (d2a5.00 1.6176 50.8r3a -401.00 +0.0015d2b 0.10 air space r3b+37.18+0.0166L2b (d3b 5.40 1.6176 50.8 r4b -550.50 +0.0011 d4 15.44 airspace (variable) r5 +477.50 +0.0013 L3 (d5 1.00 1.6228 60.0 r6 +18.46-0.0337 d6 3.70 air space r7a -43.87 -0.0185 L4a (d7a 2.90 1.8126 25.2r7b -19.00 +0.0099 L4b (d7b 1.50 1.6228 60.0 r8b +67.27 -0.0092 d8 9.01air space (variable) r9 -13.50 -0.0379 L5 (d9 1.00 1.5120 64.0 r10-30.31 +0.0168 d10 5.85 air space (variable) r11 +57.44 +0.0099 L6 (d112.40 1.5712 55.8 r12 -27.65 +0.0206
 6. A varifocal objective systemcomprising a basic multilens objective and a varifocal front attachmentfor said objective, said attachment being composed of a substantiallyfixed positive first component, an axially movable negative secondcomponent, an axially movable negative third component and a fixedpositive fourth component; said first component consisting of a negativefirst lens followed by at least one positive second lens; said secondcomponent consisting of a first and a negative second lens memberair-spaced from each other; said third component being a third negativelens member; said fourth component being a positive lens member; saidfirst component including a positive third lens L2b and a positivefourth lens L2c following said positive second lens L2a, said secondnegative lens member being a doublet composed of a negative lens L4a anda positive lens L4b, the relative numerical values of the radii r1 - r12and of the thicknesses and separations d1 - d11 of said front lens L1,said positive second lens L2a, said positive third lens L2b, saidpositive fourth lens L2c, said first negative lens member L3, saidnegative lens L4a, said positive lens L4b, said third negative lensmember L5 and said positive lens member L6, the magnitudes of theirrefractive indices ne and Abbe numbers Nu e, and the surface powersDelta n/r thereof being substantially as given in the following Table:Lenses Radii Thicknesses ne Nu e Delta n/r and separations r1 -153.40-0.0050 L1 (d1 1.80 1.7684 26.7 r2 +91.53 -0.0083 d2 1.80 air space r2a+111.98 +0.0055 L2a (d2a 4.40 1.6228 60.0 r3a -159.60 +0.0039 d2b 0.10air space r3b +132.70 +0.0047 L2b (d3b 4.40 1.6255 57.7 r4b -132.70+0.0047 d3c 0.10 air space r4c +37.18 +0.0167 L2c (d4c 4.65 1.6228 60.0r5c +102.54 -0.0060 d4 15.87 air space (variable) r5 +150.08 +0.0047 L3(d5 1.00 1.7161 53.6 r6 +16.28 -0.0439 d6 3.70 air space r7a -60.03-0.0107 L4a (d7a 1.50 1.6430 59.8 r7b +17.16 +0.0098 L4b (d7b 3.551.8126 25.2 r8b +62.14 -0.0130 d8 10.23 air space (variable) r9 -14.55-0.0345 L5 (d9 1.00 1.5020 61.2 r10 -41.81 +0.0120 d10 8.50 air space(variable) r11 +56.91 +0.0109 L6 (d11 2.40 1.6203 54.8 r12 -32.91+0.0188
 7. A varifocal objective system comprising a basic multilensobjective and a varifocal front attachment for said objective, saidattachment being composed of a substantially fixed positive firstcomponent, an axially movable negative second component, an axiallymovable negative third component and a fixed positive fourth component;said first component consisting of a negative first lens followed by atleast one positive second lens; said second component consisting of afirst and a negative second lens member air-spaced from each other; saidthird component being a third negative lens member; said fourthcomponent being a positive lens member; said first component including apositive third lens L2b and a positive fourth lens L2c following saidpositive second lens L2a, said second negative lens member being adoublet composed of a positive lens L4a and a negative lens L4b, therelative numerical values of the radii r1 - r12 and of the thicknessesand separations d1 - d11 of said front lens L1, said positive lens L2a,said positive third lens L2b, said positive fourth lens L2c, said firstnegative lens member L3, said positive lens L4a, said negative lens L4b,said third negative lens member L5 and said positive lens member L6, themagnitudes of their refractive indices ne and Abbe numbers Nu e, and thesurface powers Delta n/r thereof being substantially as given in thefollowing Table: Lenses Radii Thicknesses ne Nu e Delta n/r andseparationsr1 -155.50 -0.0048 L1 (d1 1.80 1.7616 27.3 r2 +92.16 -0.0082d2 1.60 air space r2a +116.70 +0.0053 L2a (d2a 4.80 1.6228 60.0 r3a-150.82 +0.0041 d2b 0.10 air space r3b +113.50+0.0054L2b (d3b 4.701.6228 60.0 r4b -163.85 +0.0038 d3c 0.10 air space r4c +37.18 +0.0167L2c (d4c 4.65 1.6228 60.0 r5c +102.54 -0.0060 d4 17.66 air space(variable) r5 +150.82 +0.0046 L3 (d5 1.00 1.6940 54.4 r6 +17.29 -0.0401d6 3.70 air space r7a -88.36 -0.0091 L4a (d7a 3.05 1.8126 25.2 r7b-19.64 +0.0086 L4b (d7b 1.00 1.6430 59.8 r8 +29.13 -0.0220 d8 10.75 airspace (variable) r9 -12.73 -0.0392 L5 (d9 1.00 1.4995 66.7 r10 -35.96+0.0138 d10 8.60 air space (variable) r11 +63.02 +0.0098 L6 (d11 2.401.6203 54.8 r12 -28.09 +0.0220
 8. A varifocal objective systemcomprising a basic multilens objective and a varifocal front attachmentfor said objective, said attachment being composed of a substantiallyfixed positive first component, an axially movable negative secondcomponent, an axially movable negative third component and a fixedpositive fourth component; said first component consisting of a negativefirst lens followed by at least one positive second lens; said secondcomponent consisting of a first and a negative second lens memberair-spaced from each other; said third component being a third negativelens member; said fourth component being a positive lens member; saidfirst component including a positive third lens L2b and a positivefourth lens L2c following said positive second lens L2a, said secondnegative lens member being a doublet composed of a positive lens L4a anda negative lens L4b, the relative numerical values of the radii r1 - r12and of the thicknesses and separations d1 - d11 of said front lens L1,said positive second lens L2a, said positive third lens L2b, saidpositive fourth lens L2c, said first negative lens member L3, saidpositive lens L4a, said negative lens L4b, said third negative lensmember L5 and said positive lens member L6, the magnitudes of theirrefractive indices ne and Abbe numbers Nu e, and the surface powersDelta n/r thereof being substantially as given in the following Table:Lenses Radii Thicknesses ne Nu e Delta n/r and separations r1 -137.38-0.0055 L1 (d1 2.00 1.7616 27.3 r2 +110.25 -0.0069 d2 1.80 air space r2a+188.90 +0.0033 L2a (d2a 6.85 1.6255 57.7 r3a -126.60 +0.0049 d2b 0.10air space r3b +94.06 +0.0066 L2b (d3b 7.20 1.6228 60.0 r4b -257.20+0.0024 d3c 0.10 air space r4c +48.02 +0.0129 L2c (d4c 6.75 1.6228 60.0r5c +212.40 -0.0029 d4 18.56 air space (variable) r5 +496.40 +0.0013L3(d5 1.00 1.6940 54.4 r6 +22.75 -0.0305 d6 4.50 air space r7a -137.60-0.0059 L4a (d7a 5.00 1.8126 25.2 r7b -21.05 +0.0080 L4b (d7b 1.001.6430 59.8 r8b +23.27 -0.0277 d8 11.87 air space (variable) r9 -14.74-0.0331 L5 (d9 1.00 1.4891 70.2 r10 -56.91 +0.0085 d10 13.58 air space(variable) r11 +46.49 +0.0133 L6 (d11 2.40 1.6203 54.8 r12 -44.43+0.0139